1. Field of the Invention
The present invention relates to an ultrasonic image generating method for generating an ultrasonic image based on ultrasonic echo data obtained by transmitting/receiving ultrasonic waves to/from an inspection object.
2. Description of the Related Art
In recent years, ultrasonic diagnostic apparatuses have come into wide use in medical and industrial fields. The ultrasonic diagnostic apparatuses are for noninvasively diagnosing the inside of an inspection object by transmitting/receiving ultrasonic waves to/from the inspection object.
These conventional ultrasonic diagnostic apparatuses are provided with an ultrasonic image generating method for generating an three-dimensional ultrasonic (cubic) image constructed by two-dimensional tomograms, such as radial images (cross sections perpendicular to the scan axis of an ultrasonic transducer) and linear images (cross sections horizontal to the scan axis of the ultrasonic transducer), based on ultrasonic echo data obtained by transmitting/receiving ultrasonic waves to/from the inspection object.
As such a conventional ultrasonic image generating method, for example, as shown in Japanese Unexamined Patent Application Publication No. 2000-254123, a method has been proposed by which a three-dimensional image extracted from a body cavity surface is generated in order to facilitate three-dimensionally recognizing an ultrasonic image.
In general, one problem associated with a tomogram is the “pulsation” of a human body.
Typically, the ultrasonic diagnostic apparatus performs a helical scan by causing the ultrasonic transducer to radially scan (i.e., scan perpendicularly to the scan axis of the ultrasonic transducer), and causing it to linearly scan (i.e., scan horizontally to the scan axis of the ultrasonic transducer), and thereby acquires two-dimensional tomograms such as the above-described radial image and linear image. Here, the helical scan requires a time of, e.g., about 2 to 4 sec.
However, in the above-described conventional ultrasonic image generating method, the positions of a region of interest usually causes deviation between the scan starting time and scan finishing time due to the pulsation occurring for the time period of about 2 to 4 sec during which the above-described helical scan is performed. This “deviation” causes a problem chiefly in the above-described linear image. When the extent of the deviation is too large, even if the linear image is constructed, it may not bring about a clear image.
Possible causes of the deviation in the linear image include elements shown in the following table 1 besides the pulsation.
TABLE 1CausesFeaturesPulsationAbout 70 times per min; periodic, small, andvigorous movementPeristalsisOn the order of once every several seconds;periodic, large, and slow movementFluctuation ofIrregular and slow movementProbeRespiratoryIrregular and slow movementMovement
The ultrasonic image generating method set forth in the above-described Japanese Unexamined Patent Application Publication No. 2000-254123 involves a problem in that, when the images of an organ with blood vessels running adjacently thereto are converted into a three-dimensional image, the organ shifts under the influence of the pulsation, thereby distorting the image.
In contrast to this, among the conventional ultrasonic image generating methods, a method has been proposed that attempts to eliminate the influence of the pulsation, for example, as set forth in Japanese Unexamined Patent Application Publication No. 2000-316864.
However, the ultrasonic image generating method set forth in the above-described Japanese Unexamined Patent Application Publication No. 2000-316864 has attained an effect to a certain extent on the elimination of pulsation, but the elimination effect thereof is not yet sufficient. This being the situation, a more effective ultrasonic image generating method has been demanded.
On the other hand, among the conventional ultrasonic image generating methods, a method has been proposed that attempts to stabilize ultrasonic images by determining the barycenter of a body cavity, as set forth in Japanese Patent No. 3316268.
However, the ultrasonic image generating method set forth in the above-described Japanese Patent No. 3316268 has only the effect of stabilizing two-dimensional tomograms on a monitor, and even if this method is as-is applied to an ultrasonic image with a three-dimensional spread (i.e., three-dimensional image) for eliminating the influence of pulsation, it would produce no effect.
The present invention has been made in light of the above-described situations, and aims to provide an ultrasonic image generating method capable of eliminating the influence of pulsation and acquiring high-quality ultrasonic images.